Riveting is a commonly used process for fastening parts together. There are several rivet head styles commonly utilized including flush (countersunk head), round head and universal head. The majority of rivets are produced from a ductile metal and consist of a head and a solid cylindrical shank. To fasten two or more parts together, the shank portion of a rivet is inserted into two or more properly sized, concentrically aligned holes. The rivet is then upset or squeezed to make installation permanent.
Rivets are generally installed with the intent of securing parts together for the duration of the parts' life cycle. However, parts frequently must be refastened or removed and replaced for a number of reasons including: replacing faulty component parts, replacing loose rivets, deformation or open seams between components and bulging due to trapped drill shavings or other foreign matter.
Flush rivets, in particular, pose a significant challenge for removal and replacement. The most common method for removal involves drilling through the head of a rivet then driving the shank portion out of the hole with a pin punch. Traditional techniques of rivet removal require a highly skilled drill operator in order to avoid elongation of the holes. If the holes are elongated, the holes must be enlarged to accept oversized fasteners. In many cases, parts must be scrapped because the edge distance after oversizing is not sufficient for the application. Elongation occurs because it is difficult to center and orient a drill with flush rivets.
In many hole drilling operations performed by hand drilling machines it is accepted practice to use a drill guide surrounding the cutting end of a twist drill for the purpose of stabilizing the drilling operation. Examples include the tools described in U.S. Pat. No. 1,023,002; U.S. Pat. No. 2,296,087; U.S. Pat. No. 2,360,942; U.S. Pat. No. 2,372,398; U.S. Pat. No. 3,620,635; U.S. Pat. No. 5,228,811 and U.S. Pat. No. 5,318,39.
On aircraft panels fastened with flush rivets, using a type of bit guide that seats adjacent to the perimeter of the rivet head is undesirable as it may scar and degrade the material in the countersunk region. Additionally, such a device does not control the path of the drill since it does not orient the drill perpendicular to the rivet head. On the exterior of aircraft, flush heads are commonly shaved and blended to match the skin contour. For these rivets a seam does not exist, thus it is not possible to seat a bit guide around the periphery. Since the prior art does not provide a reliable tool for establishing perpendicularity of a drill with respect to these rivet heads, a removal opening is likely to be drilled on an angle such that the periphery of the existing holes is damaged. The present invention overcomes these limitations by adapting and improving the use of drill guides.